the I m going through the docs Why do we

The empty index is just a hacky way of asking the LLM something directly.

You could also modify prompt templates for each query engine, but in general that is a bit more complicated

Can I also ask what the difference is between SQL Router Query Engine and SQL Auto Vector Query Engine? As I understand they both route between SQL data and vector data. What would be the use cases where one would fit instead of the other?

They are basically the same yea, but the router example can be combined with as many indexes as you want. The SQL Auto Vector is only two indexes.

In the router example, it shows using a Single selector, which means it will only use one sub-index. But you could also use a Multi selector which may query multiple indexes.

In general though, the SQL Auto Vector (which is also slightly deprecated, a more flexible version is SQLJoinQueryEngine), is more optimized for SQL + something else it seems

Thank you for clarifying for me. By the way, your videos are great! They help me understand better. I hope you do some more 🙂

Thanks! Definitely planning on doing more. Was travelling last week so progress was slowed haha. Hopefully 1 or 2 more this week.